The present invention relates to smoking articles such as cigarettes, and in particular to those smoking articles having a short fuel element and a physically separate aerosol generating means. Smoking articles of this type, as well as materials, methods and/or apparatus useful therein and/or for preparing them, are described in the following U.S. Pat. No. 4,708,151 to Shelar, No. 4,714,082 to Banerjee et al., No. 4,732,168 to Resce, No. 4,756,318 to Clearman et al., No. 4,782,644 to Haarer et al., No. 4,793,365 to Sensabaugh et al., No. 4,802,568 to Haarer et al., No. 4,827,950 to Banerjee et al., No. 4,854,331 to Banerjee et al., No. 4,858,630 to Banerjee et al., No. 4,870,748 to Hensgen et al., No. 4,881,556 to Clearman et al., No. 4,893,637 to Hancock et al., No. 4,893,639 to White, No. 4,903,714 to Barnes et al., No. 4,917,128 to Clearman et al., No. 4,928,714 to Shannon, No. 4,938,238 to Hancock et al., No. 4,989,619 to Clearman et al., No. 5,016,654 to Bernasek et al., No. 5,019,122 to Clearman et al., No. 5,020,548 to Farrier et al., No. 5,027,836 to Shannon et al., No. 5,027,837 to Clearman et al., No. 5,033,483 to Clearman et al., No. 5,038,802 to White et al., No. 5,042,509 to Banerjee et al., No. 5,052,413 to Baker et al., No. 5,060,666 to Clearman et al., No. 5,065,776 to Lawson et al., No. 5,067,499 to Banerjee et al., No. 5,076,292 to Sensabaugh, Jr. et al., No. 5,076,297 to Farrier et al., and No. 5,099,861 to Clearman et al., as well as in the monograph entitled Chemical and Biological Studies of New Cigarette Prototypes That Heat Instead of Burn Tobacco, R. J. Reynolds Tobacco Company, 1988 (hereinafter "RJR Monograph"). These smoking articles are capable of providing the smoker with the pleasures of smoking (e.g., smoking taste, feel, satisfaction, and the like). Such smoking articles also typically provide low yields of visible sidestream smoke as well as low yields of FTC tar when smoked.
The smoking articles described in the aforesaid patents and/or publications generally employ a combustible fuel element for heat generation and an aerosol generating means, positioned physically separate from, and typically in a heat exchange relationship with the fuel element. Many of these aerosol generating means employ a substrate or carrier for one or more aerosol forming materials, e.g., polyhydric alcohols, such as glycerin. As the substrate material is heated by the burning of the fuel element, the aerosol forming materials are volatilized and released therefrom to form an aerosol.
Some of the substrates used previously comprised heat stable materials, i.e., materials which can not burn or decompose appreciably when subjected to the heat generated by the burning fuel element. Such materials include adsorbent carbons, such as porous grade carbons, graphite, activated carbons, or non-activated carbons, and the like. Other heat stable materials include inorganic solids, such as ceramics, glass, alumina, vermiculite, clays such as bentonite, and the like.
Other substrate materials used previously have comprised cellulosic materials, e.g., paper, tobacco paper and the like, rolled or randomly gathered to provide a substrate segment having an evaporative surface and a reservoir area. As hot gases from the burning fuel element contact the evaporative surface, aerosol forming materials are depleted from therefrom, but at the same time, they are replenished through wicking action from the reservoir area. Such materials typically require a large amount of aerosol former to be present on the substrate to prevent scorching or burning.
It would be advantageous to have a substrate for smoking articles, particularly cigarettes, which, without the need for bearing excessive amounts of aerosol forming materials, would not scorch or burn appreciably during use. However, such a substrate would have to hold sufficient aerosol forming materials to provide aerosol over the 10-15 puff life of a cigarette. It would also be desirable that such a substrate would be stable during storage, i.e., the aerosol forming materials would not appreciably migrate therefrom, e.g., to the other parts of the smoking article. Finally, it would be advantageous that such a substrate would be capable of being manipulated using conventional cigarette making equipment.
These and other desirable attributes of smoking articles, and particularly cigarettes, are provided by the smoking articles of the present invention, which utilize an improved substrate as described below.